UF's main attraction is its ability to purify, separate, and concentrate target macromolecules in continuous systems. UF does this by pressurizing the solution flow. The solvent and other dissolved components that pass through the membrane are known as permeate. The components that do not pass through are known as retentate. Depending on the Molecular Weight Cut Off (MWCO) of the membrane used, macromolecules may be purified, separated, or concentrated in either fraction.

Currently, the study of UF processing occurs mainly in laboratory setups[citation needed] because it is very prone to membrane fouling caused by increased solute concentration at the membrane surface (either by macromolecular adsorption to internal pore structure of membrane, or aggregation of protein deposit on surface of membrane), which leads to concentration polarization (CP)). CP is the major culprit in decreasing permeate flux. Ultrafiltration is used as a pre-treatment step in reverse osmosis processes in many Middle Eastern countries to potable drinking water, as there is little fresh water available in those areas.